diff --git a/src/lib.rs b/src/lib.rs
index bbe13d1..b24d264 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -38,7 +38,7 @@
 
 #![deny(missing_docs)]
 #![cfg_attr(test, deny(warnings))]
-#![allow(unstable)]
+#![cfg_attr(test, allow(unstable))]
 
 extern crate "rustc-serialize" as rustc_serialize;
 
@@ -111,7 +111,7 @@ impl Value {
 
     /// Extracts the string of this value if it is a string.
     pub fn as_str<'a>(&'a self) -> Option<&'a str> {
-        match *self { Value::String(ref s) => Some(s.as_slice()), _ => None }
+        match *self { Value::String(ref s) => Some(&**s), _ => None }
     }
 
     /// Extracts the integer value if it is an integer.
@@ -138,12 +138,12 @@ impl Value {
     /// 1979-05-27T07:32:00Z
     /// ```
     pub fn as_datetime<'a>(&'a self) -> Option<&'a str> {
-        match *self { Value::Datetime(ref s) => Some(s.as_slice()), _ => None }
+        match *self { Value::Datetime(ref s) => Some(&**s), _ => None }
     }
 
     /// Extracts the array value if it is an array.
     pub fn as_slice<'a>(&'a self) -> Option<&'a [Value]> {
-        match *self { Value::Array(ref s) => Some(s.as_slice()), _ => None }
+        match *self { Value::Array(ref s) => Some(&**s), _ => None }
     }
 
     /// Extracts the table value if it is a table.
diff --git a/src/parser.rs b/src/parser.rs
index 6f4f3ce..4316df3 100644
--- a/src/parser.rs
+++ b/src/parser.rs
@@ -188,9 +188,9 @@ impl<'a> Parser<'a> {
                 let mut table = BTreeMap::new();
                 if !self.values(&mut table) { return None }
                 if array {
-                    self.insert_array(&mut ret, &keys[], Table(table), start)
+                    self.insert_array(&mut ret, &*keys, Table(table), start)
                 } else {
-                    self.insert_table(&mut ret, &keys[], table, start)
+                    self.insert_table(&mut ret, &*keys, table, start)
                 }
             } else {
                 if !self.values(&mut ret) { return None }
@@ -282,7 +282,7 @@ impl<'a> Parser<'a> {
             Some((pos, '[')) => self.array(pos),
             Some((pos, '-')) |
             Some((pos, '+')) => self.number_or_datetime(pos),
-            Some((pos, ch)) if ch.is_digit(10) => self.number_or_datetime(pos),
+            Some((pos, ch)) if is_digit(ch) => self.number_or_datetime(pos),
             _ => {
                 let mut it = self.cur.clone();
                 let lo = it.next().map(|p| p.0).unwrap_or(self.input.len());
@@ -574,7 +574,7 @@ impl<'a> Parser<'a> {
     }
 
     fn datetime(&mut self, start: usize, end_so_far: usize) -> Option<Value> {
-        let mut date = self.input[start..end_so_far].to_string();
+        let mut date = format!("{}", &self.input[start..end_so_far]);
         for _ in 0..15 {
             match self.cur.next() {
                 Some((_, ch)) => date.push(ch),
@@ -588,27 +588,27 @@ impl<'a> Parser<'a> {
                 }
             }
         }
-        let mut it = date.as_slice().chars();
+        let mut it = date.chars();
         let mut valid = true;
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
         valid = valid && it.next().map(|c| c == '-').unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
         valid = valid && it.next().map(|c| c == '-').unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
         valid = valid && it.next().map(|c| c == 'T').unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
         valid = valid && it.next().map(|c| c == ':').unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
         valid = valid && it.next().map(|c| c == ':').unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
-        valid = valid && it.next().map(|c| c.is_digit(10)).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
+        valid = valid && it.next().map(is_digit).unwrap_or(false);
         valid = valid && it.next().map(|c| c == 'Z').unwrap_or(false);
         if valid {
             Some(Datetime(date.clone()))
@@ -726,7 +726,7 @@ impl<'a> Parser<'a> {
                 _ => unreachable!(),
             }
         }
-        Some((cur, &keys.last().unwrap()[]))
+        Some((cur, &**keys.last().unwrap()))
     }
 
     fn insert_table(&mut self, into: &mut TomlTable, keys: &[String],
@@ -735,7 +735,7 @@ impl<'a> Parser<'a> {
             Some(pair) => pair,
             None => return,
         };
-        let key = key.to_string();
+        let key = format!("{}", key);
         let mut added = false;
         if !into.contains_key(&key) {
             into.insert(key.clone(), Table(BTreeMap::new()));
@@ -778,13 +778,13 @@ impl<'a> Parser<'a> {
             Some(pair) => pair,
             None => return,
         };
-        let key = key.to_string();
+        let key = format!("{}", key);
         if !into.contains_key(&key) {
             into.insert(key.clone(), Array(Vec::new()));
         }
         match *into.get_mut(&key).unwrap() {
             Array(ref mut vec) => {
-                match vec.as_slice().first() {
+                match vec.first() {
                     Some(ref v) if !v.same_type(&value) => {
                         self.errors.push(ParserError {
                             lo: key_lo,
@@ -818,6 +818,10 @@ impl fmt::Display for ParserError {
     }
 }
 
+fn is_digit(c: char) -> bool {
+    match c { '0' ... '9' => true, _ => false }
+}
+
 #[cfg(test)]
 mod tests {
     use Value::Table;
diff --git a/src/serialization.rs b/src/serialization.rs
index ebc9f39..a7ddaf3 100644
--- a/src/serialization.rs
+++ b/src/serialization.rs
@@ -203,10 +203,10 @@ impl rustc_serialize::Encoder for Encoder {
         self.emit_value(Float(v))
     }
     fn emit_char(&mut self, v: char) -> Result<(), Error> {
-        self.emit_str(v.to_string().as_slice())
+        self.emit_str(&*format!("{}", v))
     }
     fn emit_str(&mut self, v: &str) -> Result<(), Error> {
-        self.emit_value(Value::String(v.to_string()))
+        self.emit_value(Value::String(format!("{}", v)))
     }
     fn emit_enum<F>(&mut self, _name: &str, f: F)
         -> Result<(), Error>
@@ -269,7 +269,8 @@ impl rustc_serialize::Encoder for Encoder {
         -> Result<(), Error>
         where F: FnOnce(&mut Encoder) -> Result<(), Error>
     {
-        let old = mem::replace(&mut self.state, NextKey(f_name.to_string()));
+        let old = mem::replace(&mut self.state,
+                               NextKey(format!("{}", f_name)));
         try!(f(self));
         if self.state != Start {
             return Err(NoValue)
@@ -406,7 +407,7 @@ impl Decoder {
                 self.cur_field.clone()
             } else {
                 match self.cur_field {
-                    None => Some(field.to_string()),
+                    None => Some(format!("{}", field)),
                     Some(ref s) => Some(format!("{}.{}", s, field))
                 }
             }
@@ -491,7 +492,7 @@ impl rustc_serialize::Decoder for Decoder {
     fn read_char(&mut self) -> Result<char, DecodeError> {
         let ch = match self.toml {
             Some(Value::String(ref s)) if s.chars().count() == 1 =>
-                s.as_slice().char_at(0),
+                s.chars().next().unwrap(),
             ref found => return Err(self.mismatch("string", found)),
         };
         self.toml.take();
@@ -521,7 +522,7 @@ impl rustc_serialize::Decoder for Decoder {
         where F: FnMut(&mut Decoder, usize) -> Result<T, DecodeError>
     {
         let mut first_error = None;
-        for i in range(0, names.len()) {
+        for i in 0..names.len() {
             let mut d = self.sub_decoder(self.toml.clone(), "");
             match f(&mut d, i) {
                 Ok(t) => { self.toml = d.toml; return Ok(t) }
@@ -578,7 +579,7 @@ impl rustc_serialize::Decoder for Decoder {
         -> Result<T, DecodeError>
         where F: FnOnce(&mut Decoder) -> Result<T, DecodeError>
     {
-        let field = f_name.to_string();
+        let field = format!("{}", f_name);
         let toml = match self.toml {
             Some(Table(ref mut table)) => {
                 table.remove(&field)
@@ -700,8 +701,8 @@ impl rustc_serialize::Decoder for Decoder {
             Some(Table(ref table)) => {
                 match table.iter().skip(idx).next() {
                     Some((key, _)) => {
-                        f(&mut self.sub_decoder(Some(Value::String(key.to_string())),
-                                                key.as_slice()))
+                        let val = Value::String(format!("{}", key));
+                        f(&mut self.sub_decoder(Some(val), &**key))
                     }
                     None => Err(self.err(ExpectedMapKey(idx))),
                 }
@@ -730,7 +731,7 @@ impl rustc_serialize::Decoder for Decoder {
     fn error(&mut self, err: &str) -> DecodeError {
         DecodeError {
             field: self.cur_field.clone(),
-            kind: ApplicationError(err.to_string())
+            kind: ApplicationError(format!("{}", err))
         }
     }
 }
@@ -785,7 +786,7 @@ impl fmt::Display for DecodeError {
 impl StdError for DecodeError {
     fn description(&self) -> &str {
         match self.kind {
-            ApplicationError(ref s) => s.as_slice(),
+            ApplicationError(ref s) => &**s,
             ExpectedField(..) => "expected a field",
             ExpectedType(..) => "expected a type",
             ExpectedMapKey(..) => "expected a map key",
diff --git a/src/show.rs b/src/show.rs
index fcbc277..21aec1e 100644
--- a/src/show.rs
+++ b/src/show.rs
@@ -13,7 +13,7 @@ impl fmt::Display for Value {
         match *self {
             String(ref s) => {
                 try!(write!(f, "\""));
-                for ch in s.as_slice().chars() {
+                for ch in s.chars() {
                     match ch {
                         '\u{8}' => try!(write!(f, "\\b")),
                         '\u{9}' => try!(write!(f, "\\t")),
@@ -57,7 +57,7 @@ impl<'a, 'b> Printer<'a, 'b> {
             match *v {
                 Table(..) => continue,
                 Array(ref a) => {
-                    match a.as_slice().first() {
+                    match a.first() {
                         Some(&Table(..)) => continue,
                         _ => {}
                     }
@@ -69,18 +69,18 @@ impl<'a, 'b> Printer<'a, 'b> {
         for (k, v) in table.iter() {
             match *v {
                 Table(ref inner) => {
-                    self.stack.push(k.as_slice());
+                    self.stack.push(&**k);
                     try!(writeln!(self.output, "\n[{}]",
                                   self.stack.connect(".")));
                     try!(self.print(inner));
                     self.stack.pop();
                 }
                 Array(ref inner) => {
-                    match inner.as_slice().first() {
+                    match inner.first() {
                         Some(&Table(..)) => {}
                         _ => continue
                     }
-                    self.stack.push(k.as_slice());
+                    self.stack.push(&**k);
                     for inner in inner.iter() {
                         try!(writeln!(self.output, "\n[[{}]]",
                                       self.stack.connect(".")));
diff --git a/tests/valid.rs b/tests/valid.rs
index 72e9d94..628130e 100644
--- a/tests/valid.rs
+++ b/tests/valid.rs
@@ -1,7 +1,6 @@
 extern crate "rustc-serialize" as rustc_serialize;
 extern crate toml;
 
-use std::num::strconv;
 use std::collections::BTreeMap;
 use rustc_serialize::json::Json;
 
@@ -11,27 +10,22 @@ use toml::Value::{Table, Integer, Float, Boolean, Datetime, Array};
 fn to_json(toml: Value) -> Json {
     fn doit(s: &str, json: Json) -> Json {
         let mut map = BTreeMap::new();
-        map.insert("type".to_string(), Json::String(s.to_string()));
-        map.insert("value".to_string(), json);
+        map.insert(format!("{}", "type"), Json::String(format!("{}", s)));
+        map.insert(format!("{}", "value"), json);
         Json::Object(map)
     }
     match toml {
         Value::String(s) => doit("string", Json::String(s)),
-        Integer(i) => doit("integer", Json::String(i.to_string())),
+        Integer(i) => doit("integer", Json::String(format!("{}", i))),
         Float(f) => doit("float", Json::String({
-            let (bytes, _) =
-                strconv::float_to_str_bytes_common(f, 10, true,
-                                                   strconv::SignFormat::SignNeg,
-                                                   strconv::SignificantDigits::DigMax(15),
-                                                   strconv::ExponentFormat::ExpNone,
-                                                   false);
-            let s = String::from_utf8(bytes).unwrap();
-            if s.as_slice().contains(".") {s} else {format!("{}.0", s)}
+            let s = format!("{:.15}", f);
+            let s = format!("{}", s.trim_right_matches('0'));
+            if s.ends_with(".") {format!("{}0", s)} else {s}
         })),
-        Boolean(b) => doit("bool", Json::String(b.to_string())),
+        Boolean(b) => doit("bool", Json::String(format!("{}", b))),
         Datetime(s) => doit("datetime", Json::String(s)),
         Array(arr) => {
-            let is_table = match arr.as_slice().first() {
+            let is_table = match arr.first() {
                 Some(&Table(..)) => true,
                 _ => false,
             };